Pre-class Assignment

Read through section 6.1 and complete the participation activities.

Announcements

• Lab 1 is due next Tuesday Feb 7 at 11:15am. Commit code on Github and upload report to Moodle.
  • I will have optional lab hours 2pm-4pm Fri. Feb 3 in Singer 221. You can also schedule office hours with me or post on Ed.
• Office hours: by appointment (email me if none of those times work)

Learning Objectives and Outcomes

In this lecture you will:

• listen to a short lecture about how to use AnalogIn to read values from the analog pins
• work with Prof. Delano to write code to transmit samples from an ADC pin to the serial terminal

By the end of this lecture you should be able to:

• sample an analog signal using the Nucleo board
• send samples to the serial monitor and plot them in MATLAB

Lecture Content

/*
 * Copyright (c) 2017-2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0
 */

#include "mbed.h"
#include <chrono>

// Initialize a pins to perform analog input and digital output functions
AnalogIn   ain(A0);
DigitalOut dout(LED1);
Timer t1;
using namespace std::chrono;

int main(void)
{
    while (1) {
        // test the voltage on the initialized analog pin
        //  and if greater than 0.3 * VCC set the digital pin
        //  to a logic 1 otherwise a logic 0
        if (ain > 0.3f) {
            dout = 1;
        } else {
            dout = 0;
        }

        ain.set_reference_voltage(3.3);

        t1.start();
        // print the percentage and 16 bit normalized values
        printf("percentage: %3.3f%%", ain.read() * 100.0f);
        printf(" normalized: 0x%04X", ain.read_u16());
        printf(" voltage: %3.3f\\n",ain.read_voltage());
        t1.stop();
        printf("The time taken was %llu milliseconds\\n", duration_cast<milliseconds>(t1.elapsed_time()).count());
        t1.reset();
        thread_sleep_for(1000);
        
    }
}

In Class Exercises

/*
 * Copyright (c) 2017-2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0
 */

#include "mbed.h"
#include <chrono>
#include <cmath>

// Initialize a pins to perform analog input and digital output functions
AnalogIn   ain(A0);
DigitalOut dout(LED1);
Timer t1;
using namespace std::chrono;

BufferedSerial pc(USBTX,USBRX);
char buff[6]; // largest value is 65535, new line

Ticker sample;

void sampleADC(){
    unsigned short value = ain.read_u16();

    buff[0] = value/10000 + 0x30;
    value = value - (buff[0]-0x30)*10000;
    
    buff[1] = value/1000 + 0x30;
    value = value - (buff[1]-0x30)*1000;
    
    buff[2] = value/100 + 0x30;
    value = value - (buff[2]-0x30)*100;
    
    buff[3] = value/10 + 0x30;
    value = value - (buff[3]-0x30)*10;
    
    buff[4] = value/1 + 0x30;
    
    pc.write(&buff,6);
}

int main(void)
{
    buff[5] = '\\n';

    sample.attach(&sampleADC,100ms);

    while (1) {
        thread_sleep_for(100);
        
    }
}

For Next Time

Read sections 7.1 – 7.5 (they are short and don’t have participation activities).